skybow

Jim's Skybow FAQ


What's a skybow?

It's a new kind of kite that acts sort of like an anti-gravity rope---when you and

a friend at the other end hold it across the wind it pulls upward making a huge arch

in the sky.

Who is flying skybows?

Kite enthusiasts worldwide are experimenting with skybows, improving flying techniques,

design and materials.

How does it work?

It's not really a rope at all. It's a rapidly spinning ribbon. Have you ever

noticed that a dropped card or ticket stub can start spinning and glide

away from you as it falls? A skybow's ribbon is attached to swivels that

allow it to spin the same way.

So why does spinning make it go up?

That's a subtle question, but it's basically the same reason

a spinning ping-pong ball takes a curved flight. It's called the Magnus-Robins effect.

Okay, so why up instead of down?

With flat-ribbon skybows the fliers may have to help the ribbon

start spinning in the correct direction---the top of the ribbon should

spin downwind. Other skybows have creased edges and always spin

the same direction, these skybows must be set up properly in relation

to the direction of the wind. If started spinning in the wrong direction a skybow

is just as happy to spin the otherway and fly into the ground!

Why does it make that eerie sound?

The aerodynamic forces always act nearly at right angles to the ribbon face,

but the ribbon is constantly turning. This produces a rapidly varying reaction

against the air ---sound is the natural result. Since the ribbon has two faces,

the frequency of the sound is twice the spin rate.

A skybow flying well makes a howling sound reminiscent of the sound of high wind

in a pine woods, a skybow that is not entirely steady sounds like a motorcyle race,

with repeated accelerations and sudden downshifts of pitch.

Loudness increases drastically with wind speed. At 20 mph (32 km/hr) the curious

have been drawn from a quarter-mile (400m) away. The sound is very directional,

with a quiet spot near the fliers and directly behind them.

Why are there sometimes swivels in the middle of the arch, not just at the ends?

A skybow needs to spin faster where the wind is faster in order to fly high.

Multiple sections that spin idependently can accomodate differences in windspeed

along the skybow. Usually the fastest winds hit the high center of the arch.

Sometimes a single-section skybow is tapered---it's made wider in the center

than at the ends so that the high windspeeds at the center can be accomodated

when the whole ribbon is spinning at the same rpm.

How long can a skybow be?

The record so far, 1000 ft (303 m) long is held by, Mr. Big, a six section

skybow 5/8" wide (1.6 cm). Tony Frame and Jim Mallos flew Mr. Big over

the Washington Monument Grounds, Washington, DC on November 10, 1997.

[More photos of Mr. Big]
[Andrew Cations' photos of Mr. Big]

The maximum length of a skybow is proportional to the strength-to-weight ratio

of the ribbon material. There are fibers made with ten times the strength-to-weight

ratio of Mr. Big's ribbon, so skybows two miles long (3 km) may be possible.

How wide can a skybow be?

Tony Frame and I have flown skybows in widths ranging from 10mm to 25mm.

(Tell me about your experiments.)

How do you launch them?

Skybows are launched by pulling them taut across the wind. They can be launched

all at once, or in stages letting one section go up at a time.

How can I get one?

You'll need to make your own, see the builder's faq.

Jim Mallos